Devices, such as electronic devices, and particularly electronic payment devices (for example, so-called “smart cards”) may be useful for a variety of payment and other applications. Some payment products, such as those referred to as pre-authorized or offline-prepaid, rely on a balance managed by the card. The balance indicates the funds available on the card and is decreased by the transaction amount when a transaction takes place. For customer convenience, the terminal may display this balance before and after the card is debited.
In some types of infrastructure, the card is debited using a command issued by the terminal. The command data typically contains the transaction amount, while the corresponding response from the card confirms (and authenticates) that the card was debited and provides the necessary information for the clearing of the transaction.
A payment transaction often involves online authorization from the card issuer. In this case an authorization request containing transaction data and data from the payment device is sent to the issuer for authorization and a response to this request indicating the approval or decline of the transaction is sent from the issuer to the terminal which then sends the relevant issuer response data to the payment device. Typically, the bandwidth available in the authorization request and response is limited by the network and terminal infrastructure.